1. Field of the Invention
This invention relates to a call circuit for key telephone systems and particularly to a call circuit for a key telephone system in which circuit a direct station selection (hereinafter referred to as DSS) call is given priority over a station call.
2. Description of the Prior Art
Heretofore, there have been provided relays which correspond to DSS call switches operable by an operator and which are capable of detecting the actuation of the switches. The break contacts of the relays are inserted in respective normal station call routes for telephones in order to give priority to a DSS call by the operator over a normal station call. However, this prior art attempt has the drawback that detector circuits equal in number to the number of telephones become necessary and hence the overall apparatus is complicated in construction and expensive to manufacture. Furthermore, the prior art apparatus is liable to be bulky and weighty.